Here we report molecular dynamics simulation study to investigate the dynamical behaviour of acetylene adsorbed in CuBTC MOF. CuBTC has complex network structures consisting of main pores and side pockets connected by windows. Diffusivity of the acetylene molecules adsorbed in CuBTC is found to increase with increase in concentration of the acetylene molecules. It was found that average time spent in pockets by the acetylene molecules increases with increase in concentration suggesting faster saturation of the pockets. At higher concentration, acetylene molecules prefer to diffuse through the connecting windows rather than the pockets. Calculation of the potential energy landscape showed that molecules experience less energy barrier while diffusing through the connecting windows compared to that through the pockets.